Q.Frequencies in the UHF range normally propagate by means of:

Concept: Radio waves can propagate as ground waves (along the Earth's surface, used at low frequencies), sky waves (reflected off the ionosphere, used in the HF band), or space waves (travelling directly in a straight line from transmitter to receiver, or via reflection off the ground/troposphere — this is line-of-sight propagation).

Why UHF uses space waves:

• Ground waves are heavily attenuated at high frequencies because the ground absorbs the wave's energy rapidly as frequency increases — impractical at UHF.
• Sky waves require reflection from the ionosphere, which only happens up to roughly 30–40 MHz; UHF frequencies (300 MHz–3 GHz) simply pass through the ionosphere without reflecting.
• The only remaining mode is direct, straight-line (line-of-sight) propagation between transmitting and receiving antennas — this is the space wave mode, and it is exactly why UHF TV/FM/mobile transmission towers are built tall (to extend the line-of-sight range).

Eliminate ground waves (too much attenuation at high frequency) and sky waves (UHF is above the ionosphere's reflecting range); what's left is direct line-of-sight travel, i.e. space waves.

• Confusing 'surface wave' (a type of ground wave) with 'space wave' — they are different propagation modes.
• Assuming all radio communication uses sky waves, without checking whether the frequency actually falls in the ionosphere's reflective range.
• Forgetting that UHF's short range is exactly why UHF antennas/towers are built tall — it's a line-of-sight, not a sky-wave, mode.